Windows 95/98/2000:
Click on correct resolution for your display to link to the full-size image.
Wait for the image to finish loading...
After the image has finished loading, right-click on the full-size image and select "Set As Wallpaper" from the pop-up menu to make the image directly into wallpaper.

Mac OS:
Control-click on the link below and select "Download Image to Disk" (IE) or "Save this Image as ..." (Netscape).
Save the file to a location that you will remember. Then go to the Appearance Control Panel, and choose the "desktop" tab.
Click on "Place Picture ..."
Choose the picture you just saved and click on "set desktop."